1. Field of the Invention
The present invention relates generally to a heat exchanger and more specifically to a fin arrangement for a heat exchanger which is exposed to a flow of fluid medium.
2. Description of the Prior Art
In order to increase the heat exchange capacity of a heat exchanger such as an air-cooled radiator for use with automotive vehicles it has been been necessary to add fins to the tubing of the radiator through which the heated fluid is passed. To increase the heat exchange characteristics of the finning various louver arrangements have been proposed.
FIGS. 2 and 3 show one of two previously proposed arrangements disclosed in Japanese Utility Model First Provisional Publication No. 58-42579. In this first arrangement a plurality of air-scoop like louvers 10 are formed in the fin 12 to increase the interaction and contact between the cooling medium and the surfaces of the fins. These fins 12 are arranged to be elongate, folded in a serpentine configuration and disposed between adjacent conduits 14 which convey heated fluid from the upper tank to the lower one of the radiator R shown in FIG. 1.
However, as will be appreciated from FIG. 2, with this arrangement the provision of the louvers 10 reduces the clearance between the folded sections of the fins 12 and thus increases the resistance to the flow of air through the device undesirably.
FIGS. 4 to 6 shows the second of the two arrangements disclosed in the above mentioned reference. This arrangement features the provision of a plurality of triangular sub-fins 20 in a serpentine shaped fin arrangement 22. As shown in FIG. 5 the sub-fins 20 are formed in first and second groups, viz., groups A and B. The sub-fins 20 in the downstream group A are angled in a manner which tends to induce the air flowing through the radiator to strike against the upstream faces or surfaces thereof and induce some of the flow to pass through the apertures formed when the fins are pressed. On the other hand, the fins in the upstream bank or group B are angled in the reverse direction and thus tend to project into the flow in manner which increases the contact between the air and surface of the fins.
With this type of arrangement the greater the surface area and the steeper the angle at which the sub-fins 20 extend from the main fin body 22, the greater the effect. However, these requirements tend to unacceptably increase the air-flow resistance of the arrangement as a whole. Accordingly, the angle at which the fins are formed and the size thereof in this second arrangement is a compromise between flow resistance and heat exchange effectiveness.